The Botanical will feature a bar, terrace and private dining room overlooking the Palm House Conservatory and pond when it launches in mid-August.
Executive chef Lawrence Keogh has created a largely plant-based menu featuring pickled and preserved ingredients grown at Kew.
The bar will specialise in homemade plant-infused spirits and botanical cocktails such as the Kew Negroni.
It comes two months after the former Roast and The Wolseley chef took up the post overseeing the gardens’ four existing catering outlets.
Oliver Peyton, the founder of Peyton and Byrne said: “This is a really exciting new project, and we look forward to working closely with Kew to grow the ‘Why Plants Matter’ concept through the dishes we will serve and the ambient restaurant space we will create.”
The Botanical will launch in the 19th century former Museum No.1 building and cater to the garden’s 1.35m visitors a year.
It will be taking bookings for breakfast, lunch, afternoon tea and dinner every day.
Peyton and Byrne operates catering outlets at some of London's major attractions including The National Gallery, St James's Park and The Wallace Collection.
The Botanical will be its fifth venue at Kew, where it runs the Orangery Restaurant, Victoria Plaza Café, White Peaks Café and The Pavilion.
Kew was made a UNESCO World Heritage Site in July 2003 and celebrated its 250th anniversary in 2009.